How does the idea of rotating disk in the nebular model explain certain observed celestial phenomena ?

It is believed that a large cloud of dust and gas which rotated slowly, began to contract because gravitational forces. Rotation increased causing a bulge in the center. At its end stages the mass of gases that gathered in the center created the sun with the planets forming from the bulge.

Efficiency is an act of doing something

A) acceleration. this seems to be the one that makes sense.